After a morning jaunt to Allerton Park you really ought to see Monticello's downtown square. There is a lot to do there for such a little town. There are several excellent lunch options, an inexpensive train ride, and neat shops.
My favorite shop to stop at is Prairie Fire Glass on Washington Street, just off the square. The blown glass pieces for sale are really advanced work and the prices are reasonable. If you are there during from late fall through early spring you are likely to see artists at work. My dad and I chatted at length with the owners one winter afternoon and found out you can take beginners glass blowing. From the website it looks like they have expanded their class offering to include intermediate and advanced glass blowing. Check out the photo gallery.
Because of the heat, it is unlikely you'll find any glassblowing going on right now. But September 15 & 16th, Prairie Fire Glass will be exhibiting at Arts in the Park at Central Park in downtown Decatur.